Showing papers by "Emil F. Pai published in 1990"
TL;DR: The atomic models of the complex between rabbit skeletal muscle actin and bovine pancreatic deoxyribonuclease I both in the ATP and ADP forms have been determined byo X-ray analysis at an effective resolution of 2.8 Å and 3 Å.
Abstract: The atomic models of the complex between rabbit skeletal muscle actin and bovine pancreatic deoxyribonuclease I both in the ATP and ADP forms have been determined by X-ray analysis at an effective resolution of 2.8 A and 3A, respectively. The two structures are very similar. The actin molecule consists of two domains which can be further subdivided into two subdomains. ADP or ATP is located in the cleft between the domains with a calcium ion bound to the beta- or beta- and gamma-phosphates, respectively. The motif of a five-stranded beta sheet consisting of a beta meander and a right handed beta alpha beta unit appears in each domain suggesting that gene duplication might have occurred. These sheets have the same topology as that found in hexokinase.
1,802 citations
TL;DR: A mechanism for GTP hydrolysis involving mainly Gln61 and Glu63 as activating species for in‐line attack of water as well as a mechanism for rate enhancement by GAP is proposed.
Abstract: The crystal structure of the H-ras oncogene protein p21 complexed to the slowly hydrolysing GTP analogue GppNp has been determined at 1.35 A resolution. 211 water molecules have been built into the electron density. The structure has been refined to a final R-factor of 19.8% for all data between 6 A and 1.35 A. The binding sites of the nucleotide and the magnesium ion are revealed in high detail. For the stretch of amino acid residues 61-65, the temperature factors of backbone atoms are four times the average value of 16.1 A2 due to the multiple conformations. In one of these conformations, the side chain of Gln61 makes contact with a water molecule, which is perfectly placed to be the nucleophile attacking the gamma-phosphate of GTP. Based on this observation, we propose a mechanism for GTP hydrolysis involving mainly Gln61 and Glu63 as activating species for in-line attack of water. Nucleophilic displacement is facilitated by hydrogen bonds from residues Thr35, Gly60 and Lys16. A mechanism for rate enhancement by GAP is also proposed.
1,042 citations
TL;DR: Crystals of Ha-Ras p21 with caged GTP at the active site have been used to investigate the conformational changes of p21 on GTP hydrolysis and the structure of the short-lived p21-GTP complex was determined by Laue diffraction methods.
Abstract: Crystals of Ha-Ras p21 with caged GTP at the active site have been used to investigate the conformational changes of p21 on GTP hydrolysis. The structure of the short-lived p21.GTP complex was determined by Laue diffraction methods. After GTP hydrolysis, substantial structural changes occur in the parts of the molecule implicated in the interaction with GTPase-activating protein. The trigger for this process seems to be a change in coordination of the active-site Mg2+ ion as a result of loss of the gamma-phosphate of GTP.
470 citations
TL;DR: In this paper, the intensive Rontgenstrahlung eines Synchrotrons and die Renaissance der altesten rontgenbeugungstechnik, der Laue-Methode, machen es moglich: „Momentaufnahmen” bei Protein-Protein- oder Protein-Ligand-Reaktionen, so das der zeitliche Ablaut verfolgt und relativ kurzlebige Zwischenprodukte unmittel
Abstract: Die intensive Rontgenstrahlung eines Synchrotrons und die Renaissance der altesten Rontgenbeugungstechnik, der Laue-Methode, machen es moglich: „Momentaufnahmen” bei Protein-Protein- oder Protein-Ligand-Reaktionen, so das der zeitliche Ablaut verfolgt und relativ kurzlebige Zwischenprodukte unmittelbar erfast werden konnen.
4 citations